Tag Archives: hydrothermal carbonization

xxx E. Sermyagina, K. Murashko, D. Nevstrueva, A. Pihlajamäki and E. Vakkilainen
Conversion of cellulose to activated carbons for high-performance supercapacitors
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Conversion of cellulose to activated carbons for high-performance supercapacitors

E. Sermyagina¹*, K. Murashko², D. Nevstrueva¹, A. Pihlajamäki¹ and E. Vakkilainen¹

¹LUT University, Energy Technology, Laboratory of Sustainable Energy Systems, Skinnarilankatu 34, FI53850 Lappeenranta, Finland
²University of Eastern Finland, Fine Particle and Aerosol Technology Laboratory, Yliopistonranta 1 C, FI70210 Kuopio, Finland
*Correspondence: ekaterina.sermyagina@lut.fi

Abstract:

Biomass-derived activated carbons are promising materials that can be used in various applications. Current work investigates the possibilities of the cellulose-derived activated carbons in substituting the commercial alternatives for the supercapacitors’ electrodes with high efficiency, stable performance and relatively low cost. Hydrothermal carbonization (HTC) followed by chemical activation with KOH is used to convert cellulose into highly porous activated carbons. The effect of HTC parameters on the material porosity development and electrochemical properties of the electrodes is evaluated with several variations of the residence time and the weight ratio between cellulose and water during the pretreatment. The analysis shows that intensification of the HTC process (longer residence time and higher water/cellulose ratio) results in increase of the surface area of both hydrochar samples and subsequent activated carbons: with the highest surface area for the sample produced after 2 h HTC treatment with water/cellulose ratio of 6/1 – 2,645 m2 g-1. As for the electrochemical analysis, the highest values of the specific capacitance are found for the samples produced from 2 h HTC treatment: 110.3 F g-1 (water/cellulose ratio of 3/1) and 102.5 F g-1 (water/cellulose ratio of 6/1). Additionally, it is noted that electrodes produced from the samples treated during 4 h have higher impedance at low operation frequency. The present study proves the possibility to substitute commercial activated carbons with cellulose-derived materials, the porosity of which can be tuned accordingly already during the pretreatment step.

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614–623 J. Velebil, J. Malalák and J. Bradna
Mass and energetic yields of hydrochar from brewer’s spent grain
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Mass and energetic yields of hydrochar from brewer’s spent grain

J. Velebil*, J. Malalák and J. Bradna

Czech University of Life Sciences Prague, Faculty of Engineering, Department of
Technological Equipment of Buildings, Kamýcká 129, CZ 165 21 Prague, Czech Republic
*Correspondence: velebil@tf.czu.cz

Abstract:

 Brewer’s spent grain (BSG) was hydrothermally carbonized at combinations of three temperatures (180 °C, 215 °C, 250 °C) and three reaction times (2 h, 5 h, 12 h). For comparison, the corresponding barley malt was also tested at the same conditions. Elemental composition, volatile matter, ash and heating values were determined for original biomasses as well as resulting hydrochars. The mass yield of dry BSG hydrochar ranged from 45 to 73%. The energetic yield defined as retention of total lower heating value in the hydrochar on dry basis ranged from 66 to 85%. Specific lower heating value of dry material rose from 20.6 MJ kg-1 to 30.3 MJ kg-1 at the most severe conditions. Nitrogen and sulphur content in hydrochar were not strongly dependent on reaction conditions.

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